This invention relates to electrical heater systems, and more particularly to such systems in which the heating elements are thin ribbons of amorphous metallic alloys that are operated at low and moderate temperatures.
Electrical heating systems are used in numerous consumer and industrial products. Typical are hair dryers and space heaters. Most present-day electrical heating systems consist of a wire, sometimes in the form of a closely wound coil, wrapped around supports for heating the surrounding air. In some cases, such as a hair dryer, a fan is provided for forcing air movement, but in other cases convection currents are relied upon to control air movement. The required resistance of a heating element is readily determined. The power input is equal to the square of the voltage across the heating element, divided by the element's resistance. Since the full line voltage is usually applied across the heating element and the desired power is known (limited by the maximum current which can be drawn), the required resistance can be calculated.
According to the present invention, there is provided an electrical heating element made of a ribbon of amorphous metallic alloy, and an electrical heating system including these heating elements.
According to one aspect of the present invention, the heating elements are made of an amorphous metallic ribbon.
According to a second aspect of the present invention, the heating elements have a new structure and operation: the novel structure includes a large area formed by long and wide ribbons, to achieve good heat transfer to the surroundings, that is lower thermal resistance to surroundings.
The area of the heating elements and thus the thermal resistance is determined according to the desired thermal power, under the constraint of a low operating temperature, that is a temperature well below the embrittlement temperature of the amorphous alloy in use.
Thus new operating conditions are achieved, of low temperature, even for large radiated heat power. An additional novel property: fast heating constant, that is heater reaches its steady state temperature in less time.
According to a third aspect of the present invention, the heating element ribbons are manufactured using the process developed by V. Manor, that is overheating the melted (liquid) alloy before rapid quenching, to achieve more reliable heater elements with more reproducible properties.
According to a fourth aspect of the present invention, the structure of the heating elements is such as to keep the operating temperature still lower, so as not to generate benzopyrene or other unhealthy or ecologically unfavorable fumes or gases.
According to a fifth aspect of the present invention, the heating elements use lower cost alloys, that is alloys capable of withstanding oxidation only at low temperatures.
According to a sixth aspect of the invention, the electrical heating system further uses low cost insulation and support materials, that is materials intended for use at low temperatures only.
Further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description in conjunction with the drawings.